Anyone watching the daily massacre of Syrians – including babies and bystanders alongside foreign journalists – must wonder how this tragedy can end.

If history is any guide, the tipping point will arrive when enough Syrians opposed to the Assad regime and enough foreign players unite in a consensus about which universal values – humanitarianism, human rights, democracy – must be upheld, and at what cost. Only then can other interests that now divide those inside and outside Syria be set aside.

Progress toward that elusive unity took a step forward Friday when the North African nation of Tunisia – the most successful example of the Arab Spring’s democratic imperative – hosted an international meeting on Syria’s future. Players from some 60 countries (“Friends of Syria”), including the Arab League and Western powers, found further common ground on taking measures against Bashar al-Assad and his generals, who are responsible for more than 7,000 killings over the past year.

The Syrian opposition groups, however – of which there are many, inside and outside the country – appeared to remain splintered at the meeting, only hindering progress.

These groups, some armed and some pacifist, still put issues of ethnicity and religion – not to mention contending claims for legitimacy and leadership – over the higher ideals of the Arab Spring. In addition, Islamic groups scattered among the opposition complicates the task for outsiders in helping unify Syrians against the regime.

Sorting through the choices of higher ideals and embracing them has not been easy, even in the United States and Europe.

Is Syria a place to uphold humanitarianism by helping thousands of refugees in need? Turkey, as Syria’s neighbor, has started down that path. And such an ideal might argue for creating a safety zone within Syria, perhaps near the Turkish border, as the Friends of Syria meeting endorsed.

Does the ongoing killing in Syrian cities call for enforcing human rights by preventing the ongoing atrocities? A UN panel took a step in that direction Thursday by concluding that individuals “at the highest levels of government bear responsibility for crimes against humanity and other gross human rights violations.”

Or should outside powers fulfill the protesters’ original cry for democracy in Syria? On Feb. 16, the United Nations General Assembly voted 137 to 12 for Mr. Assad to step down.

Any one of these goals – democracy, human rights, humanitarianism – can, in theory, be a unifying force. As French thinker Victor Hugo said, “You can resist an invading army; you cannot resist an idea whose time has come.”

Achieving greater unity behind any one value would further isolate countries that now seek to keep Assad in power. Iran, Russia, China, and Venezuela might retreat in the face of so many countries acting in unison.

Inside Syria, too, more members of the Syrian Army might defect if they see the opposition and foreign countries coalesce around an irresistible and inspiring goal.

In many past conflicts, such as Bosnia or East Timor, the US, France, or Britain were the main players who defined the values at stake for humanity. But the grass-roots nature of the Arab Spring, and the surprising and welcome leadership of regional players such as Qatar, Turkey, and Tunisia, allow for a broader front toward taking action.

Events in coming days and weeks surrounding Syria will depend on how much any one of these ideals sinks into the thinking of more Syrians as well as into the converging constellation of foreign powers. The time is coming.